The invention relates to faceted mirrors having a plurality of mirror facets, in particular for an illumination instrument in a projection exposure system for microlithography, and here in particular for use with illumination in the extreme ultraviolet range.
Faceted mirrors comprise a plurality of mirror facets and are already known in the prior art.
Prior citation WO 03/067304 is based on manipulators which allow adjustment of the mirror facets. For example, it is known that the mirror facets have a spherical body, a mirror surface being arranged in a recess of the spherical body and the side of the spherical body remote from the mirror surface being mounted in a bearing instrument. At each of the mirror facets, a lever element is arranged on the side of the spherical body remote from the mirror surface. Adjusting means, by which the spherical body can be moved about its mid-point, engage on the lever element in a region remote from the spherical body.
With a structure of this type, it is not readily possible to achieve the requisite accuracies for relatively small mirror facets when used with radiation in the extreme ultraviolet range.
Mirror facets whose mirror surfaces are arranged on a support element are furthermore known from prior citation WO 03/067288. The support element has adjusting means by which the angular position of the mirror surface can be adjusted in at least one space direction in a plane at least approximately perpendicular to the optical axis of the mirror surface.
For further prior art, reference is made to WO 03/050586 A2, DE 100 30 495 A1, EP 0 145 243 A2 and XP-002281181 “Ion Beam and Plasma Jet Etching for Optical Component Fabrication” in Lithographic and Micromachining Techniques for Optical Component Fabrication, Ernst-Bernhard Kley, Hans Peter Herzig, editors, Proceedings of SPIE Vol. 4440 (2001).
The structure of these mirror facets is relatively elaborate, so that such faceted mirror arrangements entail an increased adjustment outlay and are relatively expensive.
Faceted mirrors need to withstand heavy thermal loads due to the radiation, especially in the extreme ultraviolet range, and the known arrangements meet the stringent requirements concerning thermal loads only to a small extent.
In respect of this, it is an object of the invention to optimize a faceted mirror, especially for ultrahigh vacuum requirements, and to provide a structure which makes do with the fewest possible parts and guarantees a reliable, long-term stable and simple structure.